This invention concerns apparatus for cutting workpieces by a laser beam to remove material by vaporization. In such apparatus, the laser beam is advanced along points forming a predetermined cutting pattern on a workpiece surface.
A widely used method for determining the extent of material removed during controlled cutting involves the use of triangulation type sensors as described in U.S. Pat. No. 5,883,356. These sensors, however, due to their triangulation operating principle, are limited in their ability to reach the bottom of the scoring produced by the cutting device. This is particularly so for narrow, deep penetrations which may be produced by cutting devices such as lasers and cutting knives. Furthermore, due to their offset mounting, these sensors are not well suited to measure the varying penetration depth that occurs during scoring at a specific location. This is especially true if the scoring penetration is in the form of partial perforations or slots. As such, the process does not lend itself to scoring the workpiece in an adaptive control mode, where both depth sensing and cutting are in registry with each other to impinge the same point on the workpiece, during the progression of scoring of the piece.
Accordingly it is an object of this invention to provide an apparatus for laser beam cutting in a manner that provides accurate adaptive process control, single-pass processing, and lower manufacturing costs.
According to the invention, the cutting of the workpiece is accomplished by apparatus including a source of a controllable cutting laser beam, which, based on feedback obtained from at least one sensor emitting a sensing beam, is controlled in intensity together with controlled relative movement between the laser and the workpiece, producing a precise, predetermined cutting penetration into the workpiece along a predetermined pattern.
In this apparatus, the laser cutting beam and sensing beam emitted from a first sensor are both directed at a surface on one side of the workpiece. A second sensor may also be positioned on the opposite side of the piece emitting a second sensor beam in opposition to the cutting laser beam. A beam combining device combines the laser cutting beam and first sensor beam together so as to have collinear segments directed at exactly the same point on the workpiece. The cutting of the workpiece is carried out by the laser beam while the piece is moved in a predetermined pattern relative to the laser. The depth of cutting of the work piece by the laser beam is controlled by real time feedback signals corresponding to the depth of the cut provided by the first sensor. To determine material thickness remaining during cutting of each point along the predetermined pattern, real time feedback from the second sensor can be provided combined with the feedback signals from the first sensor. The sensor feedback can also be utilized to control the movement of the workpiece relative to the laser beam to enhance the cutting process control.
This apparatus, due to the collinear arrangement of the impinging segments of the sensor and cutting beams, affords several advantages, including single-pass adaptive processing, cutting precision, and superior piece-to-piece repeatability. The cutting achieved is also independent of cutting depth, angle of cutting, scoring patterns, material inconsistency, material color, and surface variations.
Relative motion between the workpiece and the cutting beam to cut the piece in a predetermined pattern can be provided by different means including actuators, robots and X-Y tables.
The workpiece can have a monolayer, multilayer, or composite construction and can be scored on either side. The cutting can be continuous, intermittent or be a combination of both, and extend completely through one or more layers of the piece. The piece can be a finished part or a component which is subsequently integrated into a finished part.